The present framework for Community action in the field of water policy (Water Framework Directive, WFD) (European Commission, 2000) aims at maintaining and improving he aquatic environment in the European Union. The success in the implementation of the WFD depends on the achievement of reliable monitoring data, which assure good managing strategies and potential remediation actions in water bodies at EU-level. To obtain reliable data, water analysis laboratories must develop quality assurance (QA) systems and assure not only internal quality control (QC), but also external quality control such as regular participation in proficiency testing (PT) schemes. The European Commission finded the project "Screening method for Water data Information in support of the Water Framework Directive" from January 2004 till March 2007 (SWIFT-WFD). One of the activities undertaken in hte SWIFT-WFD project was the production of quality control tools. In this chapter, the preparation of selected water reference materials, and other quality control tools such as calibrants and multi-component standard solutions, is described. The produced materials were used in three PT schemes with the participation of a total of 94 laboratories from 21 European countries.